The Plastic Greenhouse

Polycarbonate Panels

Twin wall, UV treated polycarbonate sheets for greenhouses provide excellent clarity and heat retention. As the name implies these greenhouse plastic panels have two layers pf polycarbonate sheeting separated by flutes. This provides a double-glazing effect and improves the thermal efficiency. A 6mm thick twin-wall polycarbonate panel would have an R rating of 1.6.  Which is far superior to 3mm glass with R=0.95 or plastic sheeting at R=0.83.

Greenhouse Insulation R-Values

  • 200-micron Polyethylene Film            R=0.83 
  • 3mm Float Glass                               R=0.95 
  • 4mm Toughened Safety Glass            R=1.00 
  • 4mm Polycarbonate Twin-wall            R=1.43 
  • 6mm Polycarbonate Twin-wall       R=1.60    


The 'R' Value is the common unit of measure for the effectiveness of thermal insulation.The larger the number, the higher the insulation value and therefore the better heat retention. 

Polycarbonate panels also have a high degree of clarity with up to 80%+ of visible light getting through to the plants depending on the thickness of the panel. Panels vary in thickness from 4mm for small hobby greenhouses to 20mm for commercial growing spaces. Most domestic greenhouse kits use 6mm thick panels. Although twin wall is the most common variety used, tri-wall polycarbonate panels are also available. They are most often found in larger commercial agriculture.

Both plastic sheeting and polycarbonate panels have significant advantages over glass for greenhouses. They are both lighter in weight and far less breakable. However, they have also tended to be quite flammable.  Dripping from water condensing on the plastic has also been a cause for concern.

These problems have been addressed by most current manufacturers of these products. In particular the Israeli company Palram has developed a polycarbonate product, Sunlight Plus, that minimizes dripping and greatly retards any fire hazard.   

Palram Polycarbonate Kit

SUNLITE Plus combines high light transmission, excellent weather resistance and a special anti-drip feature needed for plant growth.

It provides an optimal cultivation environment for greenhouses. The tough multiwall polycarbonate panel structure and low weight reduce the cost needed to build supporting structures. 

The shatterproof polycarbonate plastic coupled with an integrated UV resistant, co-extruded layer yields long service periods backed up by a 10 year limited warranty.

SUNLITE Plus sheets are self-extinguishing and comply with the most demanding of international fire resistance standards defined in the field of plastics.  This makes Palram greenhouse polycarbonate panels amongst the safest plastic to use for your greenhouse plastic needs.

Main Benefits 

  • Prevents drip from condensation 
  • More light transmission during cold periods
  • up to 80% light transmission
  • UV protection on one or both sides
  • Blocks 99.9% UV radiation
  • High thermal insulation
  • Impact resistant: virtually unbreakable
  • Lightweight
  • Easy to work with and install
  • Excellent structural durability
  • Weather and UV resistant
  • High fire ratings